May 24, 2005

Most Plant Species at Risk from Global Warming

PARIS -- More than half of Europe's plant species will be threatened or classified as vulnerable by 2080 as a consequence of global warming, a study said.

The big losers will be the northern Mediterranean rim, southern Portugal and southwestern Spain and mountain regions, where vegetation will be badly hit by hotter weather and water stress, it warned.

"There will be a major impact, even under the most modest scenarios which simulate extreme restraint in increase of greenhouse gas emissions," researcher Sandra Lavorel of the Alpine Ecology Laboratory in Grenoble, France, who took part in the study, told AFP.

The researchers used a high-powered computer model that provides seven scenarios for temperature change depending on how much fossil-fuel gas is disgorged into the atmosphere.

They factored into this model the biological criteria of 1,350 species of European plants and then overlaid the result on a map to predict how Europe's vegetation might look.

"More than half of the species we studied could be vulnerable or threatened by 2080," the authors say. "We found that risks of extinction for European plants may be large, even in moderate scenarios of climate change."

The Alps are especially at risk, as it hosts many "niche" species that over millennia have adapted to thin soil and cold and may be unable to find a home elsewhere.

"There are not many higher levels in the Alps where a plant can find refuge," Lavorel said. "They are not as big as the Himalayas."

Northern European regions would lose the least species, but mainly because the loss of native plants would be partly compensated by the arrival of species that migrate from the south.

The study, published in the US journal Proceedings of the National Academy of Sciences (PNAS), was compiled by researchers from Britain, France, Portugal and Sweden, headed by Wilfried Thuiller, a Frenchman currently at the South African National Biodiversity Institute in Cape Town.

The seven scenarios, used by the UN's Intergovernmental Panel on Climate Change, foresee a global temperature rise of between 1.8 and 3.6 Celsius (3.2 to 6.4 Fahrenheit) by 2080, depending on atmospheric levels of carbon dioxide (CO2), the principal greenhouse gas.

But this overall planetary rise in heat can vary hugely according to the location, influenced by the sea, altitude, prevailing winds and landscape.

In addition, even a small rise in temperature could have a far-reaching impact on wildlife in dry regions such as the Mediterranean coastline, where habitat is already at risk from water scarcity and forest fires.

Under the gloomiest scenario -- the highest temperature rise plus the projection that no species would be able to migrate -- 22 percent of the species would become critically endangered (a decline of more than 80 percent) and two percent would become extinct by 2080.

Under the most optimist scenario -- the lowest temperature rise plus the projection that all species could migrate -- 67 percent of species would be at low risk.